Major flat spot on a golf gti 1.8 16V KR

[frenchboy]

Firstly hi to you all this is my first post,and I live and work in France as a mechanic incase anyone wonders about my name but I was born and raised in the north east of england

Right I have just got a Mk2 golf GTI 1.8 16V KR engine and my problem is when I open the second butterfly on the throttle I have quite a big flat spot and it would pop and bang if I let it(which I haven't!) but it runs and drives lovely on the first part of the throttle but when I get to the second part of the throttle massive flat spot its not so bad doing down hills but it still does it,and if I let it rev on the first part it will rev up past the normal start point of the flat spot so it is only doing it on the second part of thottle.

It is using abit of fuel aswell and it does smell of fuel out the back so could it just be the CO2 needs tweaking?

I haven't had the chance to look into it yet but going to tomorrow as I have to change the oil pump aswell.

[frenchboy]

Update,I put a CO2 tester on it yesterday and it is reading around 1.5% Co2 it should be 2.0% shouldn't it?

Also its runing on 95 unleaded at the mo not 98 which I will put in next time I put fuel in will 95 make it have a flat spot?

[raferackstraw]

give it a good service, plugs, rotor arm, dizzy cap, do oil n filter, change fuel filter n air filter, get a timing light on it and adjust c02 n idle, then look at renewing all vacuum lines, if it still got flat spot, look at fuelling, if you dont know history on it also check cambelt n static timing